In FIG. 6 to FIG. 9, a conventional chip inductor comprises a square columnar main body 21 made of an insulating material, a coil unit 25 having a linear conductor 23 and a groove 24 formed by spirally grooving a conductor layer 22 on the surface of the main body 21, an exterior unit 29 made of an insulating resin 28 applied on the surface of the coil unit 25, and an electrode unit 26 provided at the end portion of the main body 21.
Its manufacturing method comprises a first step of forming a conductor layer 22 on a square columnar main body 21 made of an insulating material, a second step of forming a coil unit 25 having a linear conductor 23 and a groove 24 by grooving the conductor layer 22 by laser 27, a third step of forming electrode units 26 at both ends of the coil unit 25, and a fourth step of forming an exterior unit 29 by coating the coil unit 25 with an insulating resin 28 and drying.
Herein, at the fourth step, while rotating the main body 21 forming the coil unit 25 in the direction of arrow A in FIG. 9(c), on the tape to which the insulating resin 28 is adhered, the insulating resin 28 is applied on the coil unit 25, and the entire circumference of the coil unit 25 is coated with the insulating resin 28.
By drying this insulating resin 28, the exterior unit 29 is formed.
In such conventional constitution, the insulating resin 28 is applied on the surface of the coil unit 25, but the insulating resin 28 was not applied in the inner part of the groove 24 of the coil unit 25.
Generally, in a very small part such as chip inductor (overall dimension being about 1 mm), the interval of adjacent linear conductors 23 in the coil unit 25 is as narrow as scores of microns, and it is hard to coat the insulating resin 28 due to effects of surface tension and others of the insulating resin 28, and coated portions and uncoated portions of the insulating resin 28 coexisted inside the groove 24.
As a result, gaps 40 were formed inside the groove 24 as shown in FIG. 7, and due to air or moisture in the gaps 40, appropriate insulation is not provided between the adjacent linear conductors 23 of the coil unit 25, and short-circuit is caused.
Also in the conventional method, since the insulating region 28 is applied on the coil unit 25 while rotating the main body 21 forming the coil unit 25 on the tape to which the insulating resin 28 is adhered, as shown in FIG. 8, the insulating resin 28 applied on the coil unit 25 forms a circular profile, while surrounding the square columnar main body 21 due to the surface tension.
As a result, the mounting surface by the exterior unit 29 is round, and when mounting a packed substrate or the like, accurate mounting is difficult, and gaps 40 are likely to be formed in the groove 24.